Railway signaling apparatus



Feb. 15, 1938. Y L. o. GRONDAH L 2,108,433

RAILWAY SIGNALING APPARATUS Fihed May 17, 1955 INVENTQR Law" 0. Groncz'alzl HIS ATTORNEY Patented Feb. 15, 1938 A UNITED STATES PATENT OFFICE RAILWAY SIGNALING APPARATUS Lars 0. Grondahl, Pittsburgh, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application May 17, 1935, Serial No. 22,052

4 Claims. (01. 24 -41) My invention relates to railway signaling appamally closed contacts of an auxiliary relay Al; ratus, and more particularly to apparatus of the and the latter relay is normally energized over a type involving track circuits. local circuit in series with the microphone and an One of the objects of my invention is to provide auxiliary battery D. The use of the auxiliary relay novel and improved means to insure the release makes it possible to design the relay to match of a track relay when a vehicle'or train enters the microphone and also removes the micro the associated section. phone resistance from the track relay circuit.

The apparatus for insuring the release of a When a train enters the section and passes the track relay set forth in the present application microphone, its resistance increases to a point 10 is somewhat similar to that set forth in my 00- where the relay Al can no longer hold its contact 10 pending application Serial No. 705,558, filed on closed. It will be apparent, therefore, that January 6, 1934, for Railway track circuit appawhether the train efficiently shunts the track reratus, and the said copending application conlay or not it will be caused to release.

tains claims which cover broadly certain features In the form of the invention covered by Fig.

of the invention described in my present applica- 3, the track circuit at the relay end includes the 15 tion. microphone M, the track relay TR, and a bal- Tn the accompanying drawing, Figs. 1 to 8, inancing resistance l6.

elusive, show various forms of track circuits each The potential of the battery 3 is greater than embodying my invention. ordinarily employed, but with that portion of the Similar reference characters refer to similar electromotive force in excess of that normally 26 parts in each of the several views. employed balanced out by an auxiliary electromo- Referring first to Fig. 1, the reference charactive force so that a smaller fractional change in ters la and lb designate the rails of a stretch of the voltage at the entering end of the track cirrailway track, which rails are divided by insucuit is required to effect release of the track lated joints ID to form. track sections, only one of relay than ordinarily required. The auxiliary 2'5 which is shown in the drawing and is designated circuit extends from the positive terminal of bat- A--\B. The track sectionA-B is provided with a tery D through resistance l8 to the lower tertrack circuit including a track relay TR conminal of resistance l6, where it joins the track f nected across the rails la and lb at one end of circuit path to the one terminal of the track '30 the section in series with a microphone M, and a relay; and from the negative terminal of battery 30 track battery 3 connected across the rails la and D through the balancing resistance IE3 at the uplb at the other end of the section. The microper terminal of which it joins the track circuit phone M is of the type which increases its resistpath to the other terminal of the track relay.

ance when a train passes over the track rail to The values of resistances l5 and I6 are such that which it is attached. A microphone of this type with proper setting of the adjustable resistance 5 is fully disclosed in Patent No. 1,834,077, issued ill the electromotive force of the track circuit December 1, 1931, to A. J. Sorensen. across the terminals of resistance l5 will exceed When a train moving in the direction indicated that of the auxiliary circuit by the potential reby the arrow enters the section AB, the vibraquired to pick up the relay.

40 tion of track rail la, caused by the train as it For example, if the track relay requires two 40 passes the microphone M, causes the microphone volts across its terminals to pick it up, the difto vibrate and its resistance to increase at the ference in potential required across resistance l5, same time that the track rails are being shunted, between the track and auxiliary circuit, Will be thereby insuring the release of the track relay two volts while the actual potential of each of TR. Once the track relay TR. has released its the respective current sources 3 and D may be 45 armature, a less effective shunt than that remuch higher. If now we assume that the relay quired to release the relay without the assistance will release when the potential across its termiof the microphone will be sufficient to prevent the nals is reduced to one volt, then in the conventrackrelay again picking up after the resistance tional track circuit this will represent a requireof the microphone is again. reduced to its normal ment of a 50% drop in voltage to effect release of 50 value. When the train clears the section, the rethe track relay. With the circuits herein providlay TR again picks up in the usual manner. ed the energization of the relay is effected by In Fig. 2, the track relay TR, instead of being two volts, and the drop in voltage required toefconnected to rails la and. lb in series with the feet the release of the relay is one volt as bemicrophone M, is connected in series with norfore. However, the track circuit potential avail- 55 able at the relay may, for example, be ten volts and. that of the auxiliary circuit, eight volts in the opposing direction. .Under these conditions, the relay is energized by a potential of two volts, as before, but a less efficient track shunt, effective to obtain a 10% drop in potential will cause the required one volt decrease in potential required to efiect release of the track relay.

In order to retain a constant relationship between the current flowing through the track relay from source D with respect to that supplied over the track circuit, ground electrodes II and I2 are connected in shunt of the battery D. These electrodes are so positioned with respect to the section AB that their shunting action on the current supplied to relay TR will be similar in its behavior with respect to changes in weather conditions to that of the ballast leakageresistance across the rails of the section on the current supplied to relay TR over the track circuit under the same weather conditions.

If the shunt placed across the rails by the train at any time becomes of sufiiciently low resistance, the current flow from source D may be augmented sufiiciently, bythe additional current which will then flow to the relay through microphone M and the wheels and axles of the train in multiple with resistance E5 to effect operation of the relay. Under such a circumstance however, the polar contact included in the controlling circuit of the relay opens and prevents premature closure of the controlling circuit resulting from the closure of its neutral contact. If desired, a neutral relay may be employed instead of a polarized relay. In such case, the resistance values and operating characteristics of the relay must be adjusted in such manner that with an efficient shunt across the track rails the current supplied to the relay from source D will still be insufficient for picking up the relay. In either of the foregoing forms of the invention, when a train clears the section current flow in the normal direction is reestablished and accordingly the relay picks up its neutral armature. Also, in the case where a polarized relay is employed, should its polar contact have been reversed, such contact is also restored to its normal position.

In Fig. 4, the principles employed in the preceding figure are shown in the form they take when alternating current is employed. In this figure the secondary S of a transformer T sup plies operating current to the rails la and lb at the exit end of the section. At the entrance end of the section, the alternating current track relay is energized from the secondary S2 of a transformer Tl. The transformer Tl has two primary windings. The winding Pl receives current from the secondary S3 of a transformer T2 in series with a choke coil 29. The transformer T2 has its primary winding connected to an alternating current source in reverse relation to the connection of the primary winding of the transformer T so that the current supplied to the primary winding P2 is at any instant substantially 180 out of phase with respect to that supplied to the primary winding Pl. The current flow through winding PI is, however, restricted sufficiently by choke coil 20 to enable the winding P2 to induce sufficient current in the secondary winding S2 to pick up the track relay when the section is unoccupied. When a train enters the section, the current flow through the winding P2 is readily reduced sufiiciently by the shunting action of the wheels and axles of the train and decrease of current required to effect the increase in the resistance of the microphone M to obtain the release of the track relay.

As in the direct current circuit application, provisions are made for as nearly as possible compensating for the effect variations in weather and moisture ballast conditions have on current flow through winding P2 by connecting one terminal of winding Pl to a ground electrode 2| direct and the other terminal thereof to a ground electrode 22 through inductance 23 and resistance 24, respectively. These ground electrode connections are position-ed as explained in connection with the description of Fig. 3, and in a similar manner maintain the relationship between the two primary windings Pi and P2 the same irrespective of variations in ballast conditions.

It may further be explained that variable inductance and resistance elements 23 and 24 enable the characteristic of the leakage path for current flowing through winding Pl to be adjusted to closely simulate that of the ballast leakage path of the current flowing through winding P2, While the value of choke coil 20 is such that with no current flowing through winding P2, that flowing through Pl will be insuflicient to operate the relay.

In the form of the invention illustrated in Fig. 5, the track relay TR is again of the alternating current type and is connected across the rails la and lb in series with a contact of the auxiliary relay Al. The auxiliary relay in this instance is held energized by battery D connected to rail lb and to the corresponding rail of the adjacent section, separated by the insulator [0.

As a vehicle enters the section a front wheel thereof momentarilybridges the upper rail joint In at location B and thereby shunts current from the relay Al which accordingly drops and opens the circuit of the track relay. The vehicle, While in the section, also maintains a shunt across the rails la and lb until the train clears the section. Once the track relay has released its armature, the shunting action of the train will ordinarily be sufficiently eifective to prevent the track relay again picking up until the train clears the section.

The arrangement of Fig. 6 differs from that of Fig. 5 only in that the section junctions are staggered and theauxiliary battery D is connected across the opposite rails of adjacent sections. The auxiliary relay Al will accordingly deenergize as the train enters the section and remain deenergized so long as a portion of the train occupies the space between the junctions of adjacent sections. After the train clears the junction the usual shunting action of the train will come into play to prevent the picking up of the track relay until the train clears the section.

In the form of the invention illustrated by Fig. 7, the usual battery feed arrangement, as illustrated in Figs. 1, 2 and 3, is employed. The track relay is also of the conventional type and is connected across the rails la and lb at the entrance end of the section in series with a photo-electric element or cell P with an appropriate shield and normally receiving light from a suitable lamp L focused toward the cell P. The light shining on the cell P enables sufiicient current to flow over the track circuit to hold the track relay energized. When a train enters the section it passes between the cell P and light L. The cell P immediately increases the resistance of the track relay circuit, thereby insuring the release of the relay in response to the shunting of the track circuit.

It will be obvious that the photo-electric cell P may, if desired, be employed to control an aux- 75 iliary relay in the same manner that such a relay is controlled by the microphone M in the disclosure of Fig. 2.

If it is desired to positively insure the dropping of-the track relay irrespective of the end of the section entered, this may be accomplished by ap plying the apparatus at both ends of the track section. In Fig. 8, such an arrangement is illustrated. In this figure an arrangement such as shown in Fig. 6 is modified by including a front contact of the A! relay in the track feed. circuit of the adjoining section B-C. It will be evident then that when a train in section A-B enters section B--C, the auxiliary relay AI will open the feed circuit to the track relay of section B- -C so that the track shunt need be only sufficiently effective to prevent the picking up of the track relay after Al has ceased to function. The movement of a train from section B--C into A-B will be effective in a manner similar to a corresponding movement as described in connection with Fig. 6, except that as the train. leaves the section the Al relay at the leaving end of the section will hold the track circuit open until nected in serieswith the track circuits illustrated by Figs. 1, 3 and 4, and the photo-electric.

Although I have herein shown and described only a few forms of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the. spirit and scope of my invention. L

Having thus described my invention, what I claim is:

1. In combination, a railway track section; a

track circuit for said section including a source of current, a trackrelay and a current limiting element; a second circuit for said relay including a second source of current and a second current limiting element with the current flow in the reverse direction to that supplied over the track circuit, means included in said second circuit for reducing the current flow therein to the extent required to prevent its interference with the actuation of said relay by current supplied over said track circuit when the section is unoccupied, the current flow over said second circuit becoming effective to aid release of said track relay when the shunting action of thewheels and axles of a train occupying said section is restricting the current flow to said track relay from said track circuit source, and means including a ground path for varying said reverse current flow in accordance with changes in ground resistance.

2. In combination with a section of railway track and a source of current connected across the rails of the section, a relay having a winding receiving energy from the track rails of the section, a circuit controlling armature adapted to be moved by the force developed by said winding, means for establishing a potential which opposes the normal track potential effective across said winding by an amount such that the resultant potential is sufficient to move said armature when the section is unoccupied, said op- I posed potential predominating over the normal potential when the section is occupied, and an auxiliary circuit including a ground connection for varying said opposed potential in response to variations in the ground resistance to maintain the unbalanced condition of said potentials constant during changes in weather conditions.

3. In combination, a section of railway track, a track circuit for said section including a main source of current and a track relay, means including an auxiliary source in the wayside for passing a current in the reverse direction to that supplied from said main source through said track relay, the magnitude of said reverse current being such that normally the track relay energization from said main source predominates sufiiciently to maintain said relay picked up, and means including a ground path for by-passing a portion of the current from said auxiliary source in accordance with variations in the ground resistance whereby when a train enters said section a small reduction in the energizer.

tion from said main source renders the reverse energization from said auxiliary source efiective to release said track relay.

4. In combination, a section of railway track,

7 a track circuit for said section including a source of current and a track relay, an impedance connected across the terminals of said track relay, means for establishing a potential drop across said impedance in the opposite direction to that established by the potential drop due to the track circuit source, the magnitude of the opposed potential drop being such that said track relay is normally maintained energized from said track circuit source, and means including a ground path for varying said opposed potential drop in accordance with changes in ground resistance whereby when a train enters said section and a slight reduction occurs in the normal energization said opposed potential drop will be effective to cause a release of said track relay.

LARS O. GRONDAI-IL. 

